According to a consideration of the present inventors, in a power supply of information equipment and the like, a further reduction in loss is required from the viewpoint of power consumption and thermal design. In particular, in a power MOSFET with low breakdown voltage (for example, breakdown voltage of 30 V) used therein, the reduction in on-resistance is required.
As a low on-resistance structure of a power MOSFET, a super junction structure is known. The super junction structure is a structure in which drain-source breakdown voltage is increased by forming a columnar semiconductor region (a column region) having an opposite polarity to an epitaxial region in the epitaxial region, and trade-off between on-resistance and drain-source breakdown voltage can be improved. For example, in Japanese Patent Application Laid-Open Publication No. 2006-196518 (Patent document 1), the column region described above is formed by multiple-stage ion implantation.